Check if a string is a palindrome - popular interview question!

IsPalindrome.cs

class Program
{
    static void Main(string[] args)
    {
        const string mom = "mom";
        const string mother = "mother";
        const int iterations = 10000;

        var sw = new Stopwatch();
        sw.Start();
        for (var i = 0; i < iterations; i++)
        {
            IsPalindrome(mom);
            IsPalindrome(mother);
        }
        sw.Stop();
        Console.WriteLine("short: " + sw.ElapsedMilliseconds);

        sw.Reset();
        sw.Start();
        for (var i = 0; i < iterations; i++)
        {
            IsPalindromeLong(mom);
            IsPalindromeLong(mother);
        }
        sw.Stop();
        Console.WriteLine("long: " + sw.ElapsedMilliseconds);

        Console.Read();
    }

    static bool IsPalindrome(string word)
    {
        if(word==null) throw new ArgumentNullException("word");
        return String.Equals(word, new string(word.Reverse().ToArray()), StringComparison.CurrentCultureIgnoreCase);
    }

    //about twice as fast
    static bool IsPalindromeLong(string word)
    {
        if (word == null) throw new ArgumentNullException("word");
        var i = 0;
        var j = word.Length - 1;
        while (true)
        {
            if (i > j)
            {
                return true;
            }
            var a = word[i];
            var b = word[j];
            if (char.ToLower(a) != char.ToLower(b))
            {
                return false;
            }
            i++;
            j--;
        }
    }
}